Receive the latest series updates in your inbox

An NBC4 I-Team investigation revealed the tricks thieves use to steal purses and other belongings from unsuspecting Southern California shoppers. Joel Grover reports for the NBC4 News at 11 on Monday, May 5, 2015. (Published Tuesday, May 6, 2014)

Updated at 10:30 PM PDT on Wednesday, May 7, 2014

Armed with nothing more than a common reusable shopping bag, a ring of thieves is stealing shoppers wallets--and identities--using a clever bag trick, at a growing number of Southern California supermarkets, an NBC4 I-Team investigation has found.

Suspects in Shopping Cart Wallet Theft Ring

"It's a nightmare. It's an ongoing nightmare," says Martha, who asked us not to use her last name. The thieves swiped Martha's wallet from her purse, which she put in her cart at Whole Foods in Del Mar.

Surveillance video obtained by the I-Team shows how it happened. A male suspect sidles up to Martha's cart, and as she turned her head to look at a display, the suspect sticks his hand in her purse, blocking her view of the cart with a reusable shopping bag.

"I was unaware of his presence," Martha told the I-Team about the suspect. "In a Whole Foods, you feel somewhat safe," she added.

Police say the male thief and his accomplices went right across the parking lot to Chase Bank, where they got a $10,000 cash advance using Martha's credit card and license. The next day, they got a moving violation on the freeway and showed police Martha's license. When they failed to show up in court, the DMV suspended Martha's license.

"I would consider them professionals," LAPD Detective Dennis Bopp told the I-Team about the theft ring.

"They're working the area from Ventura County all the way down to San Diego County," says Bopp. The I-Team has found evidence the thieves have stolen purses or wallets from shoppers at markets in at least 15 Southern California cities since last year.

Four more surveillance videos obtained by the I-Team show the ring of thieves often use the reusable shopping bag as a tool to steal. At a La Jolla Whole Foods, the ring leader and two accomplices circle near a shopper in the produce section. One of the suspects distracts a producer worker, while another walks up to the shopper, blocks her view of her cart with the shopping bag, and steals her wallet out of her purse.

"They like to go typically in the more affluent areas. The ladies will have high credit limits on their credit cards," Bopp says.

Police say thieves have a favorite supermarket chain to target shoppers: Trader Joe's, because unlike most chains, they don't put surveillance cameras in their stores.

"They're not in it to protect the consumer," says Michelle Marks about Trader Joe's. Marks filed a police report that her wallet was stolen out of the purse in her cart at Trader Joe's in Studio City April 19, when she looked away for "a second."

"I was incensed. They told me they didn't have any security cameras. They weren't helpful at all," Marks says.

Bopp says when the thieves steal a wallet, they'll find a ring member that looks similar to the victim to send to banks and stores to use the stolen credit cards and ID. "They'll even bring some props along, like a wig," Bopp said.

At least three agencies -- the LAPD, the San Diego PD, and the Ventura County Sheriff's Department -- are trying to stop this supermarket theft ring. And they're reminding shoppers not to put purses in shopping carts -- keep them on your shoulder, and men should keep credit cards and ID's in their pockets.